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Paper | Special issue | Vol 30, No. 2, 1990, pp.1009-1021
Published online, 1st January, 1970
DOI: 10.3987/COM-89-S102
Studies of as-Triazine Derivatives. XV. Intramolecular Reverse-Election Demand Diels-Alder Reaction of 1,2,4-Triazine Derivatives

Mataichi Sagi, Kunio Wada, Shoetsu Konno, and Hiroshi Yamanaka*

*Pharmaceutical Institute, Tohoku University, Aobayama, Sendai 980-8578, Japan


5,6-Diphenyl-1,2,4-triazine-3-carboxylic acid esters which have acetylenic function in the alcoholic moiety of the ester group were converted to the pyridine derivatives condensed with lactone ring by means of intramolecular reverse electron-demand Diels-Alder reaction. This type ring-transformation was applicable to the corresponding 3,5-diphenyl-1,2,4-triazine-6-carboxylic acid esters. According to the similar manner, benzofuro[2,3-b]pyridines, benzofuro[2,3-c]pyridines, and benzofuro[2,3-d]pyrimidines were synthesized in satisfactory yields. The intermediates were prepared smoothly by palladium catalyzed cross-coupling reaction of 3-, 6-, and 5-(2-iodophenoxy)-1,2,4-triazines with terminal acetylenes. The Diels-Alder reaction of 3-(2-phenylethynylphenoxy)-1,2,4-benzotriazine afforded 11-phenylbenzofuro[2,3-b]quinoline.